Diagnostic Trends in an ASD Population

Background: Research on comorbid psychiatric diagnoses in the field of autism has expanded over the last decade. Comorbid psychiatric diagnoses can manifest differently in individuals, with a wide range of behaviors and specific needs depending on the presence or combination of each disorder. Even with current research, trends over time in comorbid psychiatric disorders have been poorly described. Phenomena such as diagnostic substitution need to be more fully explored, in conjunction with describing the clinical manifestations of these co-occurring diagnoses. Individuals with co-occurring ID and autism, as well as other co-occurring psychiatric diagnoses, are distinct groups and identifying their prevalence or rate as a group is an important next step to further describing their needs. Describing these trends over time, and studying their impact, can inform temporal relationships in diagnosis trends, and inform program planning and policy implications. 

Objectives: The primary purpose of this study is to investigate prevalences of comorbid psychiatric diagnosis, examine these trends over time, and identify the diagnosis that most contributes to the increase in co-occurring diagnostic prevalence. We will also describe demographic and other factors that contribute to the differences in comorbid psychiatric diagnoses.

Methods:  Data used to identify the population with autism were collected from a large northeastern state from individuals eligible for the state Medical Assistance program. Individuals of all ages were included in the analysis, and were selected if they had any one Medicaid claim associated with an ICD-9 299.XX diagnosis in calendar years 2008-2012. Frequencies and proportions of comorbid psychiatric diagnoses were calculated and tested for significance using chi-square analysis. Multivariable logistic regression was used to determine differences in comorbid psychiatric diagnoses over time.

Results:  From 2008-2012 the prevalence of individuals with an autism having any comorbid psychiatric diagnosis increased from 47.9% to 59.4%. Across all psychiatric comorbid diagnoses, the largest increase was seen in intellectual disabilities, increasing from 6.8% to 18.3%. The most frequently diagnosed comorbid psychiatric disorder was ADD/ADHD (23%). Multivariable logistic regression analyses are ongoing to determine and control for explanatory demographic variables. 

Conclusions:  The prevalence of comorbid psychiatric diagnoses in individuals with autism who are receiving services through Medical Assistance has increased from 2008-2012. This increase in multiple psychiatric diagnoses presents a unique challenge in providing services that fit these individuals’ complex needs. As Medical Assistance coverage can depend on funding streams, it is important to determine whether or not these trends in diagnoses are a result of a better characterization of the patients’ behaviors, an increase in occurrence of these disorders, or diagnostic substitution. More research on this issue is needed to determine the extent of these diagnoses in the general population, in order to better inform diagnostic trends and service delivery in this unique population.